Newspapers are generally printed with inks that are prepared by mechanically dispersing carbon black in mineral oil (U.S. Pat. Nos. 3,199,991 and 3,330,673). The required smooth dispersion of carbon black in the ink oil is usually produced by intensively grinding the materials together in a suitable mill, such as a ball mill.
The preferred carbons for use in printing inks are finely-divided pellet, or bead, grade. In commerce, carbon pellets are manufactured by the following process: residual liquid hydrocarbon feedstock (oils or tars obtained from refinery operations) is charged into a refractory chamber which is maintained at red heat (about 2400.degree. to about 2900.degree. F.) by an ancillary burner usually fueled by gas. The residual liquid is atomized with steam in the refractory area where primary pyrolysis occurs, and secondary pyrolysis continues as the decomposition products react with oxygen that is carefully metered into the reactor as air. The reaction is then quenched to below the reaction temperature of the air-gas mixture by dropping the gas temperature, e.g., with sprays of water. The resulting fluffy carbon is then separated from the gas stream, compacted, pelletized, dried, and recovered as the carbon pellet product. A great deal of heat and combustible gases are by-products of the operation.
The carbon pellet is then transported to a printing ink manufacturing facility where it is added, along with ink vehicles, to a grinding device, such as a ball mill, to produce a smooth dispersion.
A typical carbon black reactor (as shown in FIG. 1) is about two feet in diameter and about 30 to 45 feet long. Other designs, with diameter to height ratios approaching 1:1, are also in use.